Swimming pool safety covers

ABSTRACT

Pool covers embodying the invention are formed of a very dense mesh material which ensures substantially one hundred percent shade while allowing water to pass uniformly through the cover and which is adequately strong to support the weight of an adult. The pool cover is formed of plastic fibers which are interwoven to form a dense mesh which is then subjected to a pressure and heat cycle to ensure that the resultant material has the requisite properties for allowing water to pass through at a desired rate (e.g., 0.1 to 5 gallons per square foot per minute) while blocking light (e.g., 100% shade). Thus, a self-filtering safety pool cover is formed which allows for water to pass through uniformly across its surface while blocking sunlight.

This is a divisional application claiming the benefit of co-pending U.S.patent application Ser. No. 10/387,900 filed Mar. 13, 2003.

BACKGROUND OF THE INVENTION

This invention relates to “safety” covers for swimming pools for keepingdebris from entering the pool water and preventing water puddles on theupper surface of the pool cover.

Pool covers are known and examples are disclosed, for example, in U.S.Pat. No. 3,184,764 (West) U.S. Pat. No. 4,233,695 (Rowney) and U.S. Pat.No. 5,259,078 (Crandall), the subject matter of which are incorporatedherein by reference. A principal purpose of such pool covers is toprevent entry of debris into the pool during periods of non-use, e.g.during extended periods of time from the end of one swimming season tothe beginning of the next.

A principal purpose of a “safety” pool cover is to prevent harm topersons, particularly small children and animals venturing onto the poolcover. One particular hazard is the formation of puddles on the uppersurface of the pool cover, such puddles creating drowning hazards. Thisproblem is particularly avoided by the present invention

Some pool covers are made to be water impervious, for preventing dirtywater and debris from entering the underlying pool, and are tautlysuspended over the surface of the pool. Inevitably, the cover sagsbetween its points of suspension thereby forming one or more dependentpockets which tend to deepen as rain water and debris collect on thecover. A known solution for preventing the accumulation of water in thepool cover pockets is to provide drain openings through the pool coverat the bottoms of the pockets for draining the otherwise accumulatingwater directly into the underlying pool. The drain openings are coveredby debris collecting filters whereby only relatively clean, filteredwater enters the pool.

The filtered drain openings may be included in the pool covers duringmanufacture and are located on the covers at the anticipated lowermostcover portions when the covers are mounted on the pools. A somewhatunexpected problem is that identical pool covers mounted on identicalpools will often assume different drape configurations includingdifferently located pockets of maximum sag. One cause for this, forexample, is the use of different tensions in the means, straps, springsand the like, used for mounting the pool covers on the different pools.To the extent that the existing drain openings are spaced from theactual points of maximum sag of the pool covers, pools of water collecton the covers. This is avoided in accordance with this invention.

Another principal purpose of a “safety” pool cover is that it beadequately strong to fully support the weight of a human adult walkingacross the surface of the pool mounted cover. A problem with known poolcovers of the type containing drain openings is that the presence of theopenings through an otherwise continuous pool cover provides regions ofreduced strength where tearing and rupture of the pool cover can occur.This problem is avoided by pool covers embodying the invention.

Another problem with known pool covers is that the drain openings allowsunlight to pass through the covers. The sunlight provides sufficientenergy to allow the growth of algae and like plants or fungi within thewater in the pool.

SUMMARY OF THE INVENTION

Accordingly, pool covers embodying the invention are formed of amaterial which provides a very dense mesh which ensures substantiallyone hundred percent shade while allowing water to pass (or seep) throughthe cover into the underlying pool, evenly over the entire pool coversurface, and which is adequately strong to support the weight of anadult.

In one embodiment of the invention the pool cover is formed of plasticfibers (yarns and/or threads) which are interwoven or interlaced to forma dense mesh. The dense mesh (or basic material) is then subjected to apressure and heat cycle to ensure that the resultant material has therequisite properties for allowing water to pass through at a desiredrate while blocking light. By way of example, the basic material may bespecially calendered; i.e., the woven material is passed and pressedbetween rollers(cylinders) of a calendering machine so the material isgiven a smooth and even finish by the pressure exerted by the roller ofthe calendering machine. By controlling the density of the mesh of thepool cover material (e.g., the size of the fibers extending in thevertical and horizontal direction and the number of fibers per unitarea) and the pressure and heat applied to the basic material, theresultant material develops the requisite properties when it is“calendered”; i.e., a self-filtering pool cover is formed which allowsfor water to pass through uniformly and evenly across its surface whileblocking sunlight. The pool cover may be also characterized as asafety-cover when the fibers are selected to have sufficient strength tosupport the weight of an adult.

DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view of a spool on which is rolled a plastic materialembodying the invention to form a pool cover formed of a materialembodying the invention;

FIG. 2 is a top view of a swatch of the pool cover material;

FIG. 3 is a cross sectional diagram of the pool cover shown in FIG. 1taken along line 3-3 thereof;

FIG. 4 is a cross sectional diagram of the pool cover shown in FIG. 1taken along line 4-4 thereof;

FIG. 5 is a cross sectional diagram of a section of a pool coverembodying the invention showing sunlight being blocked from passingthrough; and

FIG. 6 is a cross sectional diagram of a section of a pool coverembodying the invention showing water passing through the pool cover.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention pertains to pool covers made wholly, or partially,of a “mesh” material or fabric. An advantage of mesh covers is that theyprevent the accumulation of rain and melting snow by allowing water topass through the cover material. Allowing water to pass through the meshcover eliminates the need for a pump or a drain on or in the cover.Another advantage of mesh covers is that they are lighter in weight thansolid covers. Due to their lighter weight, mesh covers can be stretchedmore tautly over a pool surface than solid covers. Still anotheradvantage of mesh covers is that since they do not permit water toaccumulate on the cover and since they tend to be and remain tightlystretched, debris that falls on the cover tends to get blown off ratherthan having to be manually removed. Mesh covers tend to be cleaner thanother covers and to require less maintenance than solid covers over thecourse of time.

Prior art mesh covers suffer from some distinct disadvantages. The“weaves” of prior art mesh covers allows large amount of sand and siltto pass through the cover resulting in an adverse effect on the qualityand clarity of the water in the pool covered by these mesh covers. As aresult pools covered by prior art pool covers require substantial cleanup when opened for the season. Another disadvantage of known mesh coversis that they provide poor shading to sunlight. Consequently, as notedabove, algae, a microscopic plant-life commonly found in swimming poolstends to thrive during the early spring months in pools covered by meshcovers. Many homeowners who use a mesh cover also have to use a solidcover underneath the mesh cover to avoid this problem.

The disadvantages of the prior art mesh covers are overcome with meshcovers embodying the invention. A mesh cover embodying the inventionprovides 100% shading (according to the ASTM standard) and also providessand and silt filtration due to a large increase in the size of thethreads interwoven to form the mesh fabric. This is done while enablingwater due to rain and/or melting snow to pass through the cover. Themesh material of the invention has properties very similar to materialsused to make solid covers, but is lighter in weight. A mesh coverembodying the invention functions as a self-filtering cover (i.e., thefilter is built within the fabric used to from the pool cover). The meshcover allows water to pass through, eliminating the need for drains anda water pump to remove water from the cover.

An entire pool cover can be made of the mesh material or the meshmaterial may be used only in, and for, predetermined portions of a poolcover. Of significance is that a single mesh layer may be used to coverthe pool, providing lightweight protection and ease of covering anduncovering the pool.

The fabric used to manufacture a pool cover embodying the invention mayhave the following range of characteristics. [Note that in thedescription below, where applicable, the terms are as defined by, and inaccordance with, ASTM standards.]

-   -   1—Any material having the requisite strength and pliability        exhibited for example by polypropylene or any like plastic        material.    -   2—threads per inch—(a) 30-40 threads per inch along a first        direction (e.g., the horizontal or warp) direction; and (b)        10-20 threads per inch along a second direction, generally        perpendicular to the first direction, (e.g., the vertical or        fill direction).    -   3—yarn size and type—(a) the threads along one direction (e.g.,        the warp) range in size from 500-700 deniers; and (b) the        threads along the other, generally perpendicular, direction        (e.g., the fill) range in size from 2000-3500 deniers.    -   4—weight of material—may range from 7-10 ounces per sq. yd.    -   5—Grab tensile—may range (a) along the warp from 200-400 lbs        and (b) along the fill from 400-600 lbs.    -   6—Burst 600-800 pounds per sq. in. (PSI).    -   7—Tear—may range: (a) along the warp from 50-150 lbs and (b)        along the fill from 150-350 lbs.    -   8—Air flow which is a measure of the amount of water which can        flow through the cover may range from 5 to 30 cubic feet per        minute (cfm).    -   9—Shade—100% after the cover material is processed through a        heat and pressure cycle (e.g., calendered).

The various numbers and characteristics given above are by way ofexample. Note that different sizes and weights and characteristics ofthe material may be used without departing from the teachings of theinvention which is directed to high density mesh covers which allowwater to pass through while blocking sunlight, (i.e., providing 100%shade according to ASTM standard).

In accordance with the invention, a selected weave may be subjected togreater or lesser pressure and cycle through different temperatureranges to provide the desired 100% shading while allowing water to passthrough at a rate ranging from 0.1 to 5 gallons per square foot perminute.

FIG. 1 shows a spool on which is mounted a sheet of material embodyingthe invention, which material is used to form pool covers embodying theinvention. By way of example, the sheet may have a width of 6 feet and alength of more than 200 yards. Pieces of material from one or morespools may be cut and the pieces of material are then stitched togetherto form a pool cover having a desired shape for appropriately covering aselected swimming pool.

FIG. 2 is a top view of the pool cover material showing that the coveris formed by interweaving (interlacing) threads (fibers or yarn) made ofpolypropylene plastic in directions which are generally perpendicular toeach other. In a particular embodiment, material embodying the inventionwas made with 38 threads per inch along one direction (e.g., thehorizontal direction) also referred to as the “warp” and with 13 threadsper inch along the other, generally perpendicular direction (e.g., thevertical direction) also referred to as the “fill”. The size (diameter)of each thread in the “fill” (or Y) direction was approximately 3000denier (0.076 inches) and the size (diameter) of each thread in the“warp” (or X) direction was approximately 525 denier (0.026 inches).

The threads (fibers) are interwoven as shown in FIGS. 2, 3 and 4 to forma tight and strong weave. FIG. 3 is a cross-sectional diagram of thematerial taken along line 3-3 of FIG. 2. FIG. 3 shows one fiber (fi),running along the “fill” direction, weaving above selected horizontalfibers (e.g., h1, h3, h5) and then below alternate horizontal fibers(e.g., h2, h4). FIG. 4 is a cross-sectional diagram of the materialtaken along line 4-4 of FIG. 2. FIG. 4 shows one fiber (hi), runningalong the “warp” direction, weaving above selected horizontal fibers(e.g., f1, f3, f5) and then below alternate horizontal fibers (e.g., f2,f4). The thickness t_(f) of the cover so formed, as shown in FIGS. 3 and4, may range from less than 0.009 inches to more than one-half inch.Thinner and thicker pool covers may be formed so long as they have thedesired strength and other characteristics, described above. Note thatselecting fibers of a general dark colors (e.g., green, blue, black)aides in blocking light rays from passing through the cover.

After the threads are interwoven to form the basic interconnectingpattern, the resultant woven material is then subjected to a calenderingprocess. That is, the basic material, as woven, is processed in acalendering machine (not shown) having cylindrical rollers between whichthe material is passed with the rollers compressing the basic wovenmaterial. By appropriate selection of the pressure and heat applied tothe basic woven material when it is passed between the rollers duringthe calendering process, the amount of water that can pass (or seep)through the material per unit area and per unit time can be controlled.The process during which the basic material is subjected to pressure andheat (generally referred to herein as “calendering”) is also used tocontrol the amount of light that can pass through the cover. For coversembodying the invention the amount of shade provided by the processedmaterial is 100% as per the ASTM standard.

Thus, in one embodiment of the invention, a pool cover includes a basicmesh plastic material formed of threads of polypropylene material withan appropriate selection of: (a) the number of threads per unit lengthin the fill direction and in the warp direction and (b) the size of thethreads in the fill and warp direction. Also included is the processingof the basic material during which an appropriate selection of pressureand heat are applied to ensure that water can pass through the materialused to make a pool cover to prevent the accumulation of water above thecover while blocking light from passing through the cover. It should beappreciated that if the weave is made too tight and/or if thecalendering process in conjunction with the tight weave makes theprocessed material too tight, the resultant material will indeed blockthe light but the material will become partially or totally imperviousto water. That is, water will accumulate above the cover. This problemis overcome in pool covers manufactured in accordance with theinvention.

FIG. 5 illustrates that the formation of the weave after the applicationof requisite pressure and heat (e.g., calendaring) is such that lightincident on the top surface of the swimming pool cover does not passthrough, providing 100% shade according to the ASTM standard.

FIG. 6 illustrates that for the light blocking material shown in FIG. 5,water deposited on top of the cover surface passes through the cover.Consequently, in accordance with the invention, water is allowed to passthrough the cover while the amount of light which can pass through islimited and/or blocked.

A pool cover embodying the invention is intended to be draped over apool and attached to peripheral portions of the pool structure. The poolcover is of the “safety” type, and to this end, it is stretched in ataut condition over the pool and spaced from the surface of the poolwater. Any attaching arrangement (see U.S. Pat. No. 5,713,087) can beused, as well as other known or suitable attaching arrangements. Forexample, straps extending beyond the sheet edges may be used to providemeans for rigidly securing the pool cover to securing means, e.g.,pop-ups (pegs) mounted on the pool decking. Additionally, varioussprings can be used for maintaining tautness of the cover under varyingtemperature and loading conditions.

Depending upon the size of the pool cover, its shape, attaching, andstrengthening arrangements, one or more sections of the pool cover mayexperience some temporary sag and may temporarily form pockets. This maybe so during rain storms. However, in accordance with the invention,water does not accumulate above the pool cover. Rather, any water abovethe pool cover passes through the cover at a predetermined rate (e.g., 1gallon per square foot per minute). This eliminates the need for drainswhich adds labor costs and introduces weaknesses in the cover.

In accordance with the invention, the cover portion shown in FIGS. 1-6is self-draining for filtering the collected water and rapidly drainingthe collected water into the underlying pool. Of course, any debris willcollect on top of the cover. This debris can be selectively removed orbe blown away by the wind.

As mentioned, FIGS. 1-6 show a pool cover in accordance with thisinvention. A feature of the invention is that the cover is self-drainingwhile blocking sunlight from passing through.

As noted above, cutting any opening through a pool cover to provide adraining function tends to weaken the cover. “Safety” pool covers arepreferably strong enough to withstand the weight of an adult walkingacross the mounted and suspended pool cover. In many instances, toobtain the needed strength with known pool covers, extra reinforcingmeans must be provided in the pool cover adjacent to the drain openingsto compensate for the loss of strength caused by the drain openings.This is generally not necessary using pool covers of the type hereindescribed.

1. A method of forming material for a pool cover comprising the stepsof: interweaving a first set of plastic fibers lying along a firstdirection with a second set of plastic fibers lying along a seconddirection, generally perpendicular to the first direction, for forming asheet of plastic material with a mesh pattern; selecting said first setof plastic fibers to have a first density (i.e., X fibers per unit oflength) and selecting said second set of fibers to have a second density(i.e., Y fibers per unit of length) for forming a tight mesh patternenabling water to pass through the pool cover while blocking light frompassing through; and processing the material through a heat and pressurecycle for compressing the fibers such that water can pass through thematerial while light is blocked from passing through the material,providing approximately 100% shade.
 2. A method as claimed in claim 1,wherein the material is processed to provide approximately hundredpercent (100%) shade as defined in the ASTM standard.
 3. A method asclaimed in claim 1, wherein the material is processed to allow water topass through the material at a rate ranging from 0.009 to 5 gallons persquare foot per minute.
 4. A method as claimed in claim 1, wherein thematerial is sufficiently sturdy to bear the weight of an adult.
 5. Amethod as claimed in claim 1, wherein the number of threads per inchwoven along one direction is approximately three times the number ofthreads per inch interwoven in the perpendicular direction.
 6. A methodas claimed in claim 1, further including the steps of cutting andconnecting different sections of the material so it fits over anintended pool area and attaching straps to the material for securing thematerial to the pool.
 7. A method of forming a pool cover comprising thesteps of: interweaving a first set of plastic fibers lying along a firstdirection with a second set of plastic fibers lying along a seconddirection, generally perpendicular to the first direction, for forming asheet of plastic material with a mesh pattern; selecting said first setof plastic fibers to have a first density (i.e., X fibers per unit oflength) and selecting said second set of fibers to have a second density(i.e., Y fibers per unit of length) for forming a tight mesh patternenabling water to pass through the pool cover while blocking light frompassing through; processing the material such that water can passthrough the material while light is blocked from passing through thematerial, providing approximately 100% shade; and attaching straps tothe material so it can be draped over a pool and secured to the poolstructure, with the material being sturdy enough to support the weightof a human.
 8. A method as claimed in claim 7, wherein the material isprocessed to provide approximately hundred percent (100%) shade asdefined in the ASTM standard.
 9. A method as claimed in claim 7, whereinthe material is processed to allow water to pass through the material ata rate ranging from 0.009 to 5 gallons per square foot per minute.
 10. Amethod as claimed in claim 7, wherein the number of threads per inchwoven along one direction is approximately three times the number ofthreads per inch interwoven in the perpendicular direction.
 11. A poolcover comprising: a sheet of plastic material formed of plastic fiberswhich are interwoven, with a first set of fibers lying in a firstdirection having a first density and a second set of fibers lying in asecond direction, generally perpendicular to the first direction, saidfirst and second set of fibers forming a high density mesh and tightpattern enabling water to pass through the pool cover while blockinglight from passing through the cover, whereby water can not accumulateon top of the pool cover and light is blocked to prevent the growth ofalgae in the water within the pool; and wherein the material issufficiently sturdy to support the weight of an adult, when the poolcover is draped over a pool.
 12. The pool cover as claimed in claim 11,wherein the fibers are subjected to a pressure cycle and heat to modifythe characteristics of the material to allow water to pass through thematerial while blocking light.
 13. The pool cover as claimed in claim12, wherein the material provides approximately hundred percent (100%)shade as defined in the ASTM standard.
 14. The pool cover as claimed inclaim 13, wherein the material allows water to pass through the materialat a rate ranging from 0.009 to 5 gallons per square foot per minute.